LET. XXI.

OF THE SUN, MOON, AND PLANETS. 357

nation naturally supposes to be seas, continents,and the like ; and qn a more accurate inspec-tion, with a telescope, the hypothesis of plane-tary worlds receives additional confirmation.Vast cavities and asperities are observed uponvarious parts of her surface, exactly resemblingvallies and mountains; and every other appear-ance seems to indicate, that she is a body of thesame nature with our earth. We cap scarcelyhope to make optical instruments sufficientlyperfect to render animals visible at such a dis-tance ; but Mr. Herschel, whose telescopes arefar superior to any that were ever before exe-cuted, is said to have discovered a manifest vol-cano in the moon ; and if his improvements arepursued, we may, perhaps, receive indubitableproofs of her being an inhabited world.

Galileo, when he first saw this planet throughhis telescope, was struck with the singularity ofher appearance ; and being free from the preju-dices of the schools, soon discovered a strikingsimilitude between her and the earth. This istvhat Milton finely alludes to when he describesthe shield of Satan, in the first book of hisParadise Lost,

■■■■ — —" The broad circumferenceHung on his shoulders like the moon, whose orb.Through optic glass the Tuscan artist views,

At evening from the top of Fesole,

Or in Valdarno, to descry new lands,

Rivers or mountains in her spotty globe.”

A a 3

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